1. Field of the Invention
The invention relates to the field of thin film, resistive thermal printheads.
2. Description of Prior Art
Resistive thin film thermal printheads are known in the art. Such printheads having the thin film thermal printing elements disposed on and supported by glass substrates have been produced with a protective coating of silicon monoxide (SiO) over the substrate and the printing element. The silicon monoxide flim is chemically stable in the presence of thermal printing paper and other environmental conditions normally encountered by thermal printheads. However, the silicon monoxide has insufficient abrasion resistance to provide acceptable thermal printhead life.
Other prior art thermal printheads have variously been provided with protective coatings of alumina (Al.sub.2 O.sub.3), beryllia (BeO), silicon dioxide (SiO.sub.2) and borosilicate glasses. However, for various reasons, these prior art protective coatings have been found to be inappropriate for use with the thin film printheads having CrSiO resistive elements disposed on borosilicate or soda-lime glass substrates. Consequently, thermal printheads of this type require improved environmental and wear protection.